The relationship of attributed source (commercial or nonprofit) and credibility of exercise advertisements to explicit and implicit exercise-related attitudes and intentions was examined. Male and female participants (N = 227) were randomly assigned to watch health or appearance-related advertisements and then completed an implicit attitudes task and questionnaires. Health advertisements and those attributed to a nonprofit source were rated more credible. Appearance condition participants who attributed the advertisement to a nonprofit source also rated the advertisement as more credible. Participants who rated a commercial advertisement as credible reported higher implicit instrumental attitudes. Implications for exercise promotion are discussed.